When the facts change, I change my mind

Here's a great quote I've shamelessly lifted from Andrew Glyn's interesting Left critique of where we are at today, Capitalism Unleashed.

“Much of classical economics, with its [concepts of the] long-run ‘stationary state’, had a fairly well-developed limits-to-growth argument… the argument that growth that would have to stop because of limiting factors – most notably land - was definitely there.
Furthermore, the writings of our esteemed colleagues of the past are full of references to the idea that society will achieve general satiation in the distant future… With more than enough to go around, people will work less and enjoy leisure more. This vision is expressed in the writings of Marx, of Mill, of Keynes and of many others.
It can be argued that these economists underestimated the potential of technical change, or that they did not really understand human nature. Maybe that is true. But I must say it gives some pause in trying to think about the distant future. Maybe it is we who are now underestimating the potential for technical change or it is we who do not really understand human nature. If we mainstream economic thinkers reversed ourselves so strongly over the last century, why shouldn’t we reverse ourselves again over the next century?”

Martin Weitzman, Professor of Economics at Harvard, commenting in 1992 on the Limits to Growth controversy